The overall goal of this research proposal is for Stanford University, the University of Arizona, and the Kaiser Permanente Medical Centers of the South San Francisco Bay Area to continue their active involvement in Pediatric Oncology Group research activities. Stanford faculty and the University of Arizona faculty have already assumed key leadership positions in POG and have a major role in the scientific and administrative aspects of the Group. Further, Stanford and the University of Arizona have maintained excellent performance ratings in their participation in POG studies and have received commendations for the large numbers-of evaluable patients placed on therapeutic protocols. Specifically: 1) We plan to continue to enter patients on appropriate POG studies where they exist. The number of patient entries from Stanford has increased each year as appropriate POG studies become available. We anticipate that between 65 and 80 patients will be entered on frontline therapeutic studies each year from Stanford in addition to patients who will be entered from the affiliates; in addition, 30 patients or more will be entered on POG non-therapeutic studies. 2) We anticipate that the activities of individual investigators from Stanford and the University of Arizona will continue and increase during the period of this research proposal. Currently, our faculty serve as study coordinators for frontline therapeutic studies in lymphoma and leukemia, and they have coordinated and analyzed data from recently closed protocols in osteosarcoma, lymphoma, leukemia, and Ewing's sarcoma. Our faculty also serve key scientific and administrative roles as Disease Committee Chairman and Co-Chairman, Discipline Chairman and Co-Chairman, and as members of Disease and Discipline Core Committees. Thus, our faculty are in a position to influence the future direction of the scientific activities of POG. 3) We anticipate that involvement of Stanford faculty in the laboratory scientific activities of POG will continue. The laboratories of Drs. Link and Cleary have served and will continue to serve as immunology reference laboratories and molecular biologic reference laboratories for leukemia studies of POG. 4) We anticipate that non-POG related laboratory and clinical research conducted at Stanford University and its affiliates will become increasingly relevant to POG activities. Some of these activities have already been incorporated into POG laboratory and therapeutic studies and others are targeted for incorporation into future POG studies.